Adjustment of sealed reed contacts



Nov. 3, 1964 w. D. O'BRIEN 3, 7

ADJUSTMENT OF SEALED REED CONTACTS Filed Feb. 15, 1963 2 Sheets-Sheet 1INVENTOR W. 0. O'BRIEN ATTORNEY Nov. 3, 1964 w. D. O'BRIEN ADJUSTMENT 0FSEALED REED CONTACTS 2 Sheets-Sheet 2 Filed Feb. 15, 1963 FIG. 4

FIG. 3

United States Patent 3,155,478 ADJUSTMENT 0F SEALED REED CONTACTSWilliam D. GBrien, New York, N.Y., assignor to Bell TelephoneLaboratories, Incorporated, New York, N.Y., a corporation of New YorkFiled Feb. 15, 1963, Ser. No. assess 9 Claims. (Cl. 65-42) Thisinvention pertains to the fabrication of switches assembled in glasstubes and particularly relates to the process of reshaping tubes inwhich switch contacts of the reed type have been bonded. The glass tubesare reshaped in order to precisely adjust the orientation of thecontacts sealed therein.

Switches of the type to which this invention applies generally comprisetwo or more magnetically responsive, relatively flexible reed memberssealed in opposite ends of an encapsulating glass tube. The reeds aresealed in the tube in cantilevered, overlapping relation. At least twoof the reeds are so sealed as to have an air gap between theiroverlapping ends. The resulting structure is commonly known as a reedswitch. In order to establish a switching function, a magnetic field isimpressed along the length of the tube through the overlapping reeds andthe air gap therebetween. When a magnetic field is so applied, a forceof attraction is developed between the overlapping reeds. As aconsequence, the attracted reeds move together. When the reeds cometogether, electrical continuity is established therebetween. Conversely,removal of the magnetic field breaks electrical continuity byeliminating the force of attraction and permitting the reeds to moveapart. In practice it has been found that the operating characteristicsof the resulting switch depend largely on the orientation or" the reedsor contacts sealed in the tube. As a consequence, it is advantageous tobe able to adjust reed or contact orientation with precision. In thepast many methods of orienting the contacts have been used. Onerepresentative method is the so-called free-reed process. The followingsteps are illustrative of the process:

(1) Two reeds or contacts, overlapped at their tips, are suspended in amagnetic field.

(2) The overlapped reeds are surrounded by a length of glass tube openat both ends.

(3) The top of the glass tube is sealed about the uppermost reed.

(4) The lower reed is moved away from the upper reed until a proper airgap is obtained between the overlapping tips.

(5) The air gap adjustment is made permanent by sealing the bottom ofthe glass tube about the lower reed.

While the foregoing has described the assembly of a switch having onlytwo reeds, switches having more than two reeds are easily assembled in alike manner. However, it has been found that the heat required to makethe seal in step 5 adversely aifects the equilibrium relationships inthe alloy from which reeds are commonly made. As a consequence, air gapadjustments, and back contact pressure in three element switches, areuncontrollably affected.

It is, therefore, an object of this invention to improve the method inwhich sealed contact reed switches are as sembled.

A more specific object of this invention is to minimize the adverseeffects on reed orientation caused by the heat of sealing.

These and other objects are obtained in accordance with the presentinvention wherein a sealed contact reed switch is assembled in a seriesof steps as follows:

(1) Two or more reeds are sealed in the ends of a glass tube inoverlapping relation.

(2) The glass tube with the reeds sealed therein is "ice placed in aclamping member and held firmly gripped at each end while heat isapplied to the glass tube intermediate its ends until the tube materialsoftens.

(3) The clamping members are moved with respect to each other wherebythe tube is distorted along its long axis and the orientation betweenreeds or pressure between reeds is precisely adjusted.

(4) The tube is allowed to cool thereby permanently fixing the reedorientation.

Accordingly, a feature of this invention lies in the steps, and theorder in which they occur, of fabricating a sealed contact reed switchwherein the switch is assembled, sealed, and then operatively adjusted.

Another feature of this invention is the process of softening anddeforming a glass tube in order to obtain precise adjustment of theorientation of the reeds or contacts sealed therein.

This invention will be understood more clearly and fully from thefollowing detailed description when taken with reference to theaccompanying drawing in which:

FIG. 1 is a front view, partially sectioned, of one form of apparatusillustrative of this invention;

FTG. 2 is a sectioned view of a sealed contact reed switch of the typefabricated in accordance with this invention;

FIG. 3 is another front view, partially sectioned, of the apparatusshown in FIG. 1 wherein a sealed contact reed switch of the threeelement transfer type is being fabricated; and

FIG. 4 is a sectioned view of a sealed contact reed transfer switchfabricated in accordance with this invention.

Referring now to the drawing, FIG. 1 shows a switch 2h comprising reeds21 and 2-2 sealed in overlapping relation in a tube 23. The switch 2%has one end gripped in a clamp it and the other end gripped in a clamp11. The walls of the tube 23 are glass, and are protected from theclamps ill and 11 by a material 12 which may also be convenientlydesigned to absorb heat. As shown, the switch 29 has been assembled butnot adjusted. The ends 24 and 25 of the tube 23 have been sealed aboutthe reeds 21 and 22, respectively, by the sealing coils 13 and 14-. Asource of magnetic field, illustrated by a coil 15, was used to suspendthe reeds 21 and 22 by their tips in overlapping relation within theglass tube 23 until the ends 24 and 25 were sealed. The result is theillustrated switch 26.

In order to complete the fabrication of the switch 29, a heat coil 16 isused to heat and soften the glass walls of the tube 23. When the glasshas softened sufficiently, a cam 17 moves the clamp 11 laterally withrespect to the clamp 11% and subjects the tube 23 to a distorting forcealong the tube long axis. As a result, the tube 23 deforms and the tipsof the reeds 21 and 22 are separated. The resulting separation is theair gap 26 shown in FIG. 2. Froper control of the air gap 26 duringdeformation is assured by continuous monitoring by a test coil 18. Thecompleted switch 24) is shown in FIG. 2. It will be readily understoodthat adjustment of reed overlap can be accomplished in a similar mannerby applying tensile or compressive forces to the softened tube. Thematerial 12, while primarily protective, may be designed to absorb theheat generated in softening the tube 23 and may conveniently be analuminum oxide ceramic. As a consequence, the heat will be conductedaway from the reeds 21 and 22.

In FIG. 3 is shown a switch 30 of the three element transfer type whichcomprises the reeds 31a, 31b, and 32 sealed in overlapping relation in atube 33. The tube 33 is conveniently made of glass, While the reeds 31aand 32 are ordinarily made of a magnetic material. The reed Slb may ormay not be magnetic material as desired. As illusarenas/s trated, theswitch 3% has been assembled but not adjusted. In assembling the switchas shown, a contact assembly 19 was suspended in the unsealed tube 33and held in place by the magnet a. As shown in FIG. 3, the contactassembly 19 includes the reeds 31a, 31b, and 32 with a clip 4% forfirmly holding the reeds 31a and 3th a spaced distance apart. Further,the tip of the reed 32 was held in the contact assembly ll? magneticallysuspended from the tip of the reed 31a. With the contact assembly 19suspended in the tube 33, the end Ed was sealed by the sealing coil 13and the position of the reeds 31a and 31b therein was permanently fixed.In a similar manner, the free end of the reed 32 was permanently fixedin the end 35 by the sealing coil 14.

The switch 3th, as shown in FIG. 3, is completed in a manner identicalto the completion of the switch 2d shown in FIGS. 1 and 2. The clamp Alholds one end of the tube 33 while the clamp 11 holds the other end. Theheating coil 16 softens the tube 33 and a distorting force is appliedthereto by the cam 11. The air gap 36b, shown in FIG. 4, issubstantially determined by the air gap 35a and the test coil 18 is usedto monitor contact pressure between the reeds 32 and 31b. The completedswitch 3b is shown in FIG. 4.

It is to be understood that the above-described arrangements are merelyillustrative of the operation of the principles of the invention. It isexpected that numerous other arrangements may be devised by thoseskilled in the art without departing from the spirit and scope of theinvention.

What is claimed is:

1. The method of making a switch having reed contacts sealed in a glasstube, said tube having a long axis, comprising the steps of sealing aplurality of reed contacts in the ends of a glass tube in overlappingrelation to one another in the plane of said long axis, clamping eachend of the sealed tube in a suitable clamping member, heating a portionof the tube intermediate its ends until said portion becomes softened,and deforming said tube while said portion is soft by moving oneclamping member with respect to the other a spaced distance in adirection perpendicular to the long axis of said tube whereby theorientation of overlapping reed contacts is adjusted.

2. The method of making a switch in accordance with claim 1 wherein thestep of sealing a plurality of reed contacts in the ends of said glasstube comprises sealing a first reed contact in one end of said tube andsealing a second reed contact in the other end of said tube in anoverlapping relation with said first reed.

3. The method of making a switch in accordance with claim 1 wherein thestep of sealing a plurality of reed contacts in the ends of said glasstube comprises sealing first and second reed contacts parallel to oneanother in one end of said tube and sealing a third reed contact in theother end of said tube in an overlapping relation be tween said firstand second reed contacts.

4. The process of adjusting the orientation of contacts in anencapsulating tube having a long axis comprising the steps of sealing atleast one contact in each end of said tube, heating said encapsulatingtube until the tube material softens sufiiciently to permit distortionof said material, and thereafter distorting said tube until the desiredorientation of contacts is obtained.

5. The process of adjusting the orientation of contacts sealed in anencapsulating tube in accordance with claim 4 wherein the contactssealed in the ends of said tube are spaced in overlapping relationtherein.

6. The process of adjusting the orientation of contacts sealed in anencapsulating tube having a long axis in accordance with claim 5 whereinone end of said tube is distorted with respect to the other end in adirection perpendicular to the long axis of said tube.

7. The process of adjusting the orientation of contacts sealed in anencapsulating tube having a long axis in accordance with claim 5 whereinsaid tube is heated and softened adjacent the area of contact overlap.

8. The method of adjusting the orientation of the contacts of a reedswitcn, said switch having oppositely extending overlapping reedslongitudinally sealed in a glass envelope, that comprises applying aclamp to each end of the envelope, softening an intermediate portion ofthe envelope, moving one clamp with respect to the other a controlleddistance while said portion is soft to distort the envelope and move anassociated reed sealed therein, and then hardening the softened portionof the envelope to retain the distortion.

9. The method of claim 8 in which the controlled distance is measured tospace the contacts of the particular switch under adjustment from oneanother in their required relative positions.

References Cited in the file of this patent UNITED STATES PATENTS2,635,391 Essig Apr. 21, 1953 2,675,496 Umglert et al. Apr. 13, 19542,882,648 Hofgaard et al. Apr. 21, 1959

1. THE METHOD OF MAKING A SWITCH HAVING REED CONTACTS SEALED IN A GLASSTUBE, SAID TUBE HAVING A LONG AXIS, COMPRISING THE STEPS OF SEALING APLURALITY OF REED CONTACTS IN THE ENDS OF A GLASS TUBE IN OVERLAPPINGRELATION TO ONE ANOTHER IN THE PLANE OF SAID LONG AXIS, CLAMPING EACHEND OF THE SEALED TUBE IN A SUITABLE CLAMPING MEMBER, HEATING A PORTIONOF THE TUBE INTERMEDIATE ITS ENDS UNTIL SAID PORTION BECOMES SOFTENED,AND DEFORMING SAID TUBE WHILE SAID PORTION IS SOFT BY MOVING ONECLAMPING MEMBER WITH RESPECT TO THE OTHER A SPACED DISTANCE IN ADIRECTION PER-